LCL filters have been widely used for grid-connected inverters. However, the problem that how time delay affects the stability of digitally controlled grid-connected inverters with LCL filters has not been fully studied. In this paper, a systematic study is carried out on the relationship between the time delay and stability of single-loop controlled grid-connected inverters that employ inverter current feedback (ICF) or grid current feedback (GCF). The ranges of time delay for system stability are analyzed and deduced in the continuous s -domain and discrete z -domain. It is shown that in the optimal range, the existence of time delay weakens the stability of the ICF loop, whereas a proper time delay is required for the GCF loop. The present work explains, for the first time, why different conclusions on the stability of ICF loop and GCF loop have been drawn in previous studies. To improve system stability, a linear predictor-based time delay reduction method is proposed for ICF, while a time delay addition method is used for GCF. A controller design method is then presented that guarantees adequate stability margins. The delay-dependent stability study is verified by simulation and experiment.

Delay-Dependent Stability of Single-Loop Controlled Grid-Connected Inverters with LCL Filters

This paper proposes a novel decoupling scheme for a bearingless permanent-magnet synchronous motor (BPMSM) to achieve fast-response and high precision performances and to guarantee the system robustness to the external disturbance and parameter uncertainty. The proposed control scheme incorporates the neural network inverse (NNI) method and 2-degree-of-freedom (DOF) internal model controllers. By introducing the NNI systems into the original BPMSM system, a decoupled pseudo-linear system can be constituted. Additionally, based on the characteristics of the pseudo-linear system, the 2-DOF internal model control theory is utilized to design extra controllers to improve the robustness of the whole system. Consequently, the proposed control scheme can effectively improve the static and dynamic performances of the BPMSM system, as well as adjust the tracking and disturbance rejection performances independently. The effectiveness of the proposed scheme has been verified by both simulation and experimental results.

High-Performance Control for a Bearingless Permanent-Magnet Synchronous Motor Using Neural Network Inverse Scheme Plus Internal Model Controllers

Bearingless permanent-magnet (PM) synchronous motors (BPMSMs) are a new type of machines combining the characteristics of conventional PM synchronous motors and magnetic bearings. With ever-increasing concerns on applications, such as high-speed electric machines, canned pumps, high-speed-precision mechanical processing, aeronautics and astronautics, flywheel energy storage, life science, vacuum technique, and semiconductor and biotechnology industries, there is a fast growing interest in BPMSMs. In this paper, after a general description of the generation principle of radial suspension forces, a comprehensive overview of BPMSMs is presented, with particular emphasis on mathematical models, motor topologies, and control strategies. Moreover, several possible development trends of the BPMSM are also discussed.

Overview of Bearingless Permanent-Magnet Synchronous Motors

Industrial information integration engineering (IIIE) is a set of foundational concepts and techniques that facilitate the industrial information integration process. In recent years, many applicat...

A Survey on Industrial Information Integration 2016–2019

This paper explores a composite hierarchical antidisturbance control (CHADC) scheme for the resonance vibration suppression of a high-speed rotor system supported by active magnetic bearings (AMBs) in the magnetically suspended double-gimbal control moment gyroscope (MSDGCMG). The rotor dynamics with a fictitious integral term is introduced to meet the steady-state performance requirements. Resonance disturbances caused by harmonic drive transmission and gyroscopic torque disturbances caused by gimbal motions are also analyzed. The augmented composite AMB system with two types of disturbances and nonlinear electromagnetic dynamics is developed. Then, a disturbance observer is constructed and a stability analysis of the closed-loop system is performed using a Lyapunov approach. Simulation results show that the exogenous disturbance can be estimated and compensated with the appropriate control parameters. Rotor run-up experiments demonstrate that the proposed method has a good performance for disturbance rejection of harmonic drive resonance vibrations under the excitation of coupling torques. The gyroscopic torque disturbances with the bounded norm can also be attenuated effectively.

Composite Hierarchical Antidisturbance Control for Magnetic Bearing System Subject to Multiple External Disturbances

To effectively reject the influence of gyroscopic effects and gimbal movement on system stability and precision for a single-gimbal magnetically suspended control moment gyro (SGMSCMG), this paper proposes a new control strategy combining an inverse system method and internal model control. The SGMSCMG is modeled using both analytic relationships and experimental data, and its inversion is implemented in a current-mode approach. The common problems associated with the current-mode linearization are successfully handled via compensation filters and internal model controllers. The effectiveness and superiority of this proposed strategy have been demonstrated by both simulation and experimental results.

High-Precision Control for a Single-Gimbal Magnetically Suspended Control Moment Gyro Based on Inverse System Method

To radically eliminate the influence of gyroscopic effects on system stability and to improve the performances of high-precision, fast-response for the high-speed magnetically suspended rotor system in a control moment gyro, this paper proposes a control strategy that combines inverse system method and internal model control. The stability and robustness problems induced by current-mode linearization have been successfully solved by introducing phase-lead compensation and internal model controller. The effectiveness and superiority of the proposed strategy have been demonstrated by both simulation and experimental results.

Decoupling Control of Magnetically Suspended Rotor System in Control Moment Gyros Based on an Inverse System Method

To effectively reject the influence of digital control delay on system bandwidth and stability in pulsewidth-modulation H-bridge unipolar switching power amplifiers for magnetic bearings and to overcome the disadvantages of the traditional linear predictive control, this paper presents a current-sensing resistor design to include current derivation. The proposed solution can realize predictive current control by the proportional-differential current-sensing resistor networks. The common problems associated with the digital control delay are successfully resolved by the proposed method. Moreover, compared to the traditional linear prediction, the proposed one not only shortens the calculation time of the digital signal processor but also increases the tracking precision and significantly reduces the current noise. Analysis, simulation, and experimental results are presented to demonstrate the effectiveness and superiority of the proposed method.

Current-Sensing Resistor Design to Include Current Derivative in PWM H-Bridge Unipolar Switching Power Amplifiers for Magnetic Bearings

To achieve the high-accuracy and high-bandwidth attitude-rate measurement and control integration of spacecraft, a novel method based on a magnetically suspended control and sensitive gyroscope (MSCSG) configuration is proposed in this paper. MSCSGs are employed as both actuators and attitude-rate sensors. First, the structure and principle of a MSCSG is given and its modeling is established. Second, the attitude-rate measurement method based on a four-cross configuration is proposed. The corresponding attitude decoupling control law of spacecraft and the steering law of the MSCSGs have been further designed. Compared with the traditional attitude-rate measurement methods, the proposed one entirely preserves the inertial coupling moment items and cross-coupling moment items in the resolution of attitude rate by making full use of the dynamic information of the configuration. Thus, the measurement precision can be greatly improved, and the traditional tension between the accuracy and bandwidth can be well alleviated. The proposed method also enlarges greatly the attitude control bandwidth by the microgimbal moment, providing a new method for high-frequency vibration suppression. Semiphysical simulation results demonstrate the correctness and superiority of the proposed method.

Attitude-Rate Measurement and Control Integration Using Magnetically Suspended Control and Sensitive Gyroscopes

To adaptively reduce the influence of phase lag of traditional current mode switching power amplifiers on system stability and static and dynamic performances for magnetic bearing systems, this paper proposes a new, simple, and effective phase-lead compensation strategy based on unsymmetrical current sampling resistance network. The common problems associated with the existing phase-lead compensation methods for magnetic bearing power amplifiers are successfully handled via this method without additional hardware or software resources. The effectiveness and superiority of this proposed strategy have been demonstrated by both simulation and experimental results.

Yuan Ren

Papers

High-Precision Control for a Single-Gimbal Magnetically Suspended Control Moment Gyro Based on Inverse System Method

Decoupling Control of Magnetically Suspended Rotor System in Control Moment Gyros Based on an Inverse System Method

Current-Sensing Resistor Design to Include Current Derivative in PWM H-Bridge Unipolar Switching Power Amplifiers for Magnetic Bearings

Attitude-Rate Measurement and Control Integration Using Magnetically Suspended Control and Sensitive Gyroscopes

Self-Adaptive Phase-Lead Compensation Based on Unsymmetrical Current Sampling Resistance Network for Magnetic Bearing Switching Power Amplifiers